The Envisat AATSR Level 1B Brightness Temperature/Radiance product (RBT) contains top of atmosphere (TOA) brightness temperature (BT) values for the infra-red channels and radiance values for the visible channels, on a 1-km pixel grid. Values for each channel and for the nadir and oblique views occupy separate NetCDF files within the Sentinel-SAFE format, along with associated uncertainty estimates. Additional files contain cloud flags, land and water masks, and confidence flags for each image pixel, as well as instrument and ancillary meteorological information. This AATSR product [ENV_AT_1_RBT] in NetCDF format stemming from the 4th AATSR reprocessing, is a continuation of ERS ATSR data and a precursor of Sentinel-3 SLSTR data. It has replaced the former L1B product [ATS_TOA_1P] in Envisat format from the 3rd reprocessing. Users with Envisat-format products are recommended to move to the new Sentinel-SAFE like/NetCDF format products. The 4th reprocessing of ENVISAT AATSR data was completed in 2022; the processing updates that have been put in place and the expected scientific improvements have been outlined in full in the _$$User Documentation for (A)ATSR 4th Reprocessing Products$$ https://earth.esa.int/documents/20142/37627/QA4EO-VEG-OQC-MEM-4538_User_Documentation_for__A_ATSR_4th_Reprocessing_Level_1.pdf .